Investigation of heat transfer enhancement using hemispherical turbulators in a double-pipe regenerative heat exchanger with phase change material

Improving energy efficiency is crucial for minimizing environmental impact and lowering operational expenses across a variety of industrial processes. This study explored the impact of a novel designed hemispherical turbulator configuration on the melting process of RT35 phase change material (PCM) within a double-pipe heat exchanger. The validated numerical model was simulated in ANSYS Fluent, revealing that increasing the Reynolds number from 200 to 1000 improved heat exchanger effectiveness by 15.8% due to enhanced fluid mixing and a thinner thermal boundary layer, promoting effective convective heat transfer. The addition of turbulators further boosted performance, increasing the heat transfer surface area by 13.4% and NTU by 47%, resulting in a 26% increase in effectiveness at Re = 200. However, as the Reynolds number increased, the effect became less significant. At Re = 1000, only a 15.6% improvement was observed, indicating that in the absence of turbulators, the development of the hydrodynamic boundary layer is primarily influenced by the Reynolds number. The distance between the turbulators (L) gradually decreased from 25 to 5 mm, leading to an overall enhancement of 4.1% in the effectiveness of the heat exchanger. Additionally, the effect of turbulator size (D) was evaluated, and a gradual reduction in turbulator diameter from D = 20 mm to D = 2.5 mm resulted in a 3.5% increase in heat exchanger effectiveness. The analysis of flow characteristics and geometric configurations demonstrated a notable improvement in heat transfer performance. These findings underscore the potential for further enhancing heat exchanger efficiency through the refined design of turbulence-promoting elements and the strategic integration of phase change materials.